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1260-100/101 Adapt-a-Switch Carrier Module User Manual
B-2
then flow through the Mezzanine as follows: The signals enter the Mezzanine on P2A (P2, row A).
The Mezzanine connects them to J2A. The jumper assembly then connects them to J2C. The
Mezzanine connects them to P2C, which connects to the VXI backplane. The Bridge then
connects to these signals using its P2 connector.
Unlike the 1260-Series switch modules, it is not necessary to install the Bus Grant Jumper
Assembly (P/N 405951-003) on connector J1 when the Option-01T is not installed. This is because
the Mezzanine provides the same connections on P1B. However, installing the Bus Grant Jumper
Assembly causes no problems.
Power Distribution
The backplane distributes power from the Mezzanine and Bridge to the six plug-in slots.
Signals
The backplane provides a signal path between the plug-ins and the Bridge. All communications
signals are connected in parallel to all six plug-ins, except LBOARDSEL1 through LBOARDSEL6.
These six signals route to their respective plug-in slots, and identify which plug-in is currently
addressed.
The backplane also provides an analog bus. This bus consists of four pairs of PCB traces that
daisy-chain from one plug-in to the next, connecting to all six slots in parallel. Each pair of traces is
impedance-matched to 100 ohms, and is routed for maximum isolation and minimum crosstalk.
Bridge PCB Assembly
Local Bus Signal Routing
The Bridge provides the circuitry to interface between the plug-ins and the Option-01T. It receives
the local bus signals from the Option-01T on connector P2A. The zero-ohm resistors R20 through
R31 allow the signals to reach J2A, without the use of a Local Bus Jumper Assembly. From J2A,
the signals go to the interface circuitry.
DIP switches S1 and S2 allow the Option-01T to be daisy-chained to the next VXI module to the
right. If all segments of DIP switches S1 and S2 are closed, the local bus signals will also go to
P2C, which connects to the VXIbus backplane. In this case, the VXI module immediately to the
right of the 1260-100 Carrier has access to the local bus signals from the Option-01T. If the
module to the right of the 1260-100 Carrier is not meant to be controlled by the Option-01T, then all
segments of DIP switches S1 and S2 should be open.
The local bus signals LBUSC00S through LBUSC09S are differential. U2 converts LBUSC00S
through LBUSC07S to TTL levels. LBUSC08S and LBUSC09S are a bidirectional differential pair.
U3 and U4 receive and drive these signals, respectively.
Reset Circuit
U7 is a voltage monitor used to reset the Bridge and plug-ins at power turn-on. At power turn-on, it
drives LLOGICRST low for approximately 130ms. It then takes LLOGICRST high and leaves it
high, 5V power drops below 4.5V.
Summary of Contents for 1260-100
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